#include<cstdio>//uncle-lu
#include<cstring>
#include<algorithm>
template<class T>void read(T &x)
{
	x=0;int f=0;char ch=getchar();
	while(ch<'0'||ch>'9') { f|=(ch=='-'); ch=getchar(); }
	while(ch<='9'&&ch>='0') { x=(x<<1)+(x<<3)+(ch^48); ch=getchar(); }
	x = f ? -x : x;
	return ;
}

const int mod = 998244353;
int n;
int line[1010];
long long int ans, F[1010][40010];

int main()
{
	read(n);
	for (int i = 1; i <= n; i++) 
		read(line[i]);

	for (int i = 2; i <= n; i++) 
	{
		for (int j = i-1; j >= 1; j--) 
		{
			F[i][line[i] - line[j] + 20000] = (F[i][line[i] - line[j] + 20000] + F[j][line[i] - line[j] + 20000] + 1) % mod;
			ans = (ans + F[j][line[i] - line[j] + 20000] + 1) % mod;
		}
	}

	printf("%lld", (ans+n)%mod);
	return 0;
}
